Monomic is a library I wrote for connecting the Monome 40h to Processing. If you happen to have a Monome around, give it a whirl.

For you open source fiends, the source is available at GitHub. MIT license, baby.

MaxLink is a library for plugging Max/MSP and Processing together. It has since been semi-superceded by EasyOsc, but feel free to use what you like.